High-temperature water injection



lilih'hb "iihi Eiihliiii; SEARESH iihllllii United States Pat ent3,465,826 HIGH-TEMPERATURE WATER INJECTION Paul L. Terwilliger, FoxChapel Borough, Pa., assignor to Gulf Research & Development Company,Pittsburgh,

Pa., acorporation of Delaware 5 quate to introduce the desired amount ofheat into the N Drawing, Fil d O t, 19, 1967, S N 676,612 formation, thedirection of pressure differential between Int. Cl. E21b 43/24, 43/26the well and the formation is reversed and the formation US. Cl. 1663034 Claims fluids produced through the well. In one embodiment of thisinvention, the water discharged from the heater is substantiallysaturated and the pressure on the water is ABSTRACT OF THE DISCLOSUREthereafter increased by means of a pump to provide a A method of heatingan oil-bearing subsurface forma- Pressure high gh f ffaethfe thefol'matiefl- I tion to increase the rate of flow of oil therefrom inwhich The Water he lhleeted 1S heated a temperature water at atemperature of 500 to 700 F. is displaced above m a heater caliahle ofwlthstehdlhg a P d a 11 d i h f ti at a rate causing 15 sure in excessof the saturat1on pressure of water at the f t i of h f r ati Thepressure on the h temperature to wh1ch the water 1s heated. A fired.heater water is maintained at a level which will maintain the Whleh theWater 15 eh'eulated h h 15 P water in the liquid phase while it is inthe well. Larger ferred- When'the pfedhehve formehon penetrated y thequantities of heat can be delivered to the formation by well to bestimulated 15 Father Shallow, e p at the hot water at the conditionsspecified than by steam. a depth of 2,000 feet less, the Water y be P pto the desired pressure for fracturing the formation before being heatedto a temperature of 500 F. or higher. Ordinarily a pressure in the rangeof about 0.6 to 0.85 This lhvehhoh relates. to a method for lhcrehslhgp.s.i. per foot of depth is required to fracture formations. rate ofprodhchoh of oh from Wells h more parhch' Water heaters suitable foroperation in an oil field and larly to a method for thermal shmhlahoh ofWells penecapable of heating water to the desired temperature andtrating underground reservoirs contain ng viscous oils. of withstandingany desirable pressure can be obtained A methhd that h been. usedIncreasing the rate without difiiculty. Pressures of 5000 p.s.i. causeno diffihf produchoh of oh.wehs 18 9 dlspiace steam .dowh the culty andeven higher pressures can be obtained. In conweh and i l h Into theoh'heahhg fhhhahhh' After trast, steam generators suitable for oil fieldoperation are the steam in ect on has continued for a period longlimited to a maximum pressure of approximately 2500 enough to increasethe temperature of the well and at psi Because of the low density ofSteam the pressure least a portion of the underground reservoir, thepressure Supplied by the static head of Steam above the formation withinthe well is decreased to allow fluids to fiow from is relatively smalLthe fohhhhoh mtg the W The hot water is displaced down the well and intothe The thermhl shmulahoh by Steam lhlechoh Increases oil-bearingformation at a rate higher than the oil in the the productivity of wellsin several ways. The high temformation can flow outwardly through thenaturally perature of the h melts Paraihh and the Steam h curringpassages in the formation. In this manner, the cohdehsed Water .removethe paraihh and h h deposhed formation is fractured to provide channelscapable of shhds from the h The l h heals the oh h the forma- 40delivering the hot water outwardly into the formation for hoh andthereby-xedhces Its vlscohhy' The 01 1 h q substantial distances fromthe Well. The rate of injection more readily P h h formahoh when thedhechoh required for fracturing can be readily determined. Beforeprhssure dlhfehehhal 1S revershdi Large decrhases m a fracture has beencreated, the rate of displacement of l h h posslhle when the 1h reserve"a liquid into the fracture is substantially proportional to hlgh h hencethe method 15 parhchlahy hh the pressure applied to the liquid. After afracture is h Shmulhhhg pehetrahhg reservohs cohtahhhg created,increases in the rate of injection do not result in vlscouh Addlhohahythe Water Fesulhhg h cohany substantial increase in the pressure. It isdesirable to dehsahoh of the Sleam m the fhrmahoh occhplhs a displacethe hot water downwardly through tubing in the tion of the space in theformation and thereby increases wen rather than through casing, todecrease loss of heat the phessure m the formahoh' to formations betweenthe productive formation and the It IS hsuahy rehommehded t thedlsplahed ground surface. The actual rate of displacement of hot dowhweh and Into a forhlahoh be superheated to water to fracture theformation will depend on the percrease the amount of heat in each poundof the steam. meabflity and strength of the formation. A rate in the h hi however a process 15 de range of 1 to 20 barrels per minute may berequired. The scribed m which a mlxture of steam and waier fracture canbe initiated with cold water which is foltaining relatively minoramounts of water 15 dlsplaced lowed y the hot Water- If g flow rates arerequired down h Weill ahd mto the underground forinauoh' The to initiatefracturing, it may be desirable to bypass the water is mixed with thesteam only to provide a means water heater initially g gisphthhg of thesohds or Soluble Salts in the boiler Displacement of heat into formationis continued for 66 W21 er. 0 The thermal stimulation of wells by steaminjection is i sgfg ggf a gi 51:2 :2 ig gifiggt gi a h g fg limited touse in relatively shallow formations because fluids sufficiently thatthe fluids will flow readily to the the high pressure existing in deeperformations cannot be Well on reduction in pressure in Well The length ofproduced in boilers suitable for use in oil fields. Because time thatin.ecfion is continued will debend upon the of the high compressibilityof incl-Easing the pre? characteristic s of the oil reservoir such asthe thickness igt s e gei ivs i he i e shl f super eated steam ls of theoil sands, the viscosity reduction required for ac. This inventionresides in a method for the thermal ceptable P l rateS, the Wellspacing, etc. and the stimulation of wells in which water is heated to atemamelmt of h h f deslred- It 15 usually deslrahle perature of at least500 F. and preferably in the range 70 continue the in ection of hotwater for at least two weeks of 550 to 700 F. at a pressure exceedingthe saturation pressure of water at the highest temperature attained3,465,826 Patented Sept. 9, 1969 by the water. The hot water is thendisplaced down a well and into an oil-bearing formation at a pressurehigh enough to fracture the formation. After continuing to inject thehot water into the formation for a period adebefore turning the wellaround and producing formation fluids. Continued injection of hot waterfor periods as .long as two months before reversing the direction offlow can be used. After injection of the hot water has been completed,the pressure within the Well is reversed to cause flow from theformation into the well. The reversal of flow can follow immediately theinjection of hot water, or the well may be shut in for a period to allowdissemination of heat more widely through the formation before flow fromthe formation to the well is begun.

The method of this invention permits the delivery of heat intosubsurface formations at higher rates than are possible by the injectionof steam. At temperatures above 500 F., the difference between theenthalpy of saturated steam and saturated water decreases rapidly. Thehigh density of water produces a high static head in the well at thelevel of injection into the formation that is available to increase therate of flow of water from the wellhead to the productive formation. Thehigher density of water also reduces the velocity through the welltubing required for delivery of a given number of pounds of hot fluidinto the formation. Although the amount of heat that can be releasedfrom a pound of steam is substantially higher than the amount of heatthat can be released by a pound of Water, the number of pounds of waterthat can be de livered into the formation with a given wellhead pressureis enough greater than the number of pounds of steam to allow anincreased delivery of heat to the formation by means of the hot water.Because of the higher pressure at which Water heaters can operate ascompared to steam generators, a further increase in rate of heatdelivery is possible by using higher wellhead pressures for hot Waterinjection. Moreover, because steam delivered into the formationcondenses, the volume of injected fluids in the formation at completionof the heating step is higher when water is used as a heating medium.

The increased rate of delivery of heat possible by hot water as comparedwith steam is illustrated by the following example.

In a Well penetrating a formation at a depth of 2000 feet, a bottom holepressure of 2000 p.s.i. is required to fracture the formation. Themaximum operating pressure for the steam generator is 2500 p.s.i. Thedensity of steam at 2250 p.s.i. and 652 F. is 6.5 lbs/cu. ft. A columnof that steam 2000 feet high has a static head of 6.5/144 2000=90 p.s.i.At a bottom hole pressure of 2000 p.s.i. for the fracturing operation,the pressure drop in the tubing from the wellhead is AP=2500+902000=590p.s.i.

AP per 100 feet of 1ength=30=C C C V. From the Crane Company Piping Bookfor 2-inch schedule 40 tubmg Hg==enthalpy of saturated steam at 2500p.s.i.=1091 Hr=enthalpy of saturated water at reservoir temperature=7013,000X24 (109l--70)=322 10 B.t.u./day

If hot water (liquid) is displaced down the well into the formation:

The density of water at 2500 p.s.i. and 668 F.=35 lbs/cu. ft.

Static head of the Water=35f144 2000=486 p.s.i.

AP in tubing:2500+486-2000=986 p.s.i.

For an estimated flow rate of 10,000 b./d.:

1 .:MQKM. 24 X 3600 X 0. 785 X4.

=30 ftjsec. 1 '1 *Craft, Holden & Graves; Well Design; Drilling andProduction, 1962.

Hw=enthalpy of water at 2500 p.s.i. and 688:730;

11,500 b./d. 350 #/b. (73070)=2660 10 B.t.u./

day

N is Reynolds number d is pipe diameter, inches U is velocity, ft./sec.

p is density, gal.

u is viscosity, cps.

f is friction factor L is length, ft.

As shown by the above calculations, the displacement of hot water allowsinjection of 2660 10 B.t.u./day into the formation whereas with steamgenerating equipment capable of operating at the same pressure only 32210 B.t.u. can be supplied to the formation by the injection of steam.The injection of hot water makes possible further increases in heatinjection by pumping the hot water to higher pressures either beforedelivery to, or after leaving, the heater. Increasing pressure on steamafter it is generated is not feasible because of its highcompressibility. Injection of the hot water at a rate high enough tofracture the formation minimizes displacement of oil away from the welland causes delivery of heat to portions of the formation remote from thewell.

The requirement that the hot water be injected at a rate high enough tocause fracturing will usually insure a pressure in the well high enoughto prevent vaporization of the water in the well. If the temperature ofthe water at the level at which it enters the formation is 500 F., apressure of 700 p.s.i. is adequate to prevent vaporiza-= tion of thewater.

I claim.

1. A method of increasing production of oil from an oil-bearingsubsurface formation comprising pumping water down a well and into theoil-bearing formation at a rate causing creation of a fracture in theformation, heating the water to a temperature of 500 to 700 F. beforedelivery of the water into the well, the pressure on the water beinghigh enough to maintain the water in the liquid phase until it isdischarged from the well into the oil-bearing formation, continuing theinjection of water into the formation for a period adapted to transfer adesired quantity of heat to the oil-bearing formation, lowering thepressure in the well to a pressure lower than the pressure in theoil-bearing formation, and producing liquids flowing from the formationinto the well.

2. A method as set forth in claim 1 in which the well is shut in aftercompletion of the injection of hot water and before commencingproduction of formation fluids through the well for a period to increasedissemination of heat through the formation.

3. A method of heating an oil-bearing formation penetrated by a well tostimulate flow of oil therefrom come prising displacing water down thewell and into the formation at a. rate causing initiation of a fracturein the formation, displacing down the Well water at a temperature in therange of 500 to 700 F. and at a pressure adapted to maintain the waterin the liquid phase while in the well at a rate adapted to hold thefracture open, continuing the injection of the hot water at a rateadapted to hold the fracture open for a period adapted to deliver thedesired quantity of heat to the formation, reducing the pressure in thewell to a pressure lower than the pressure in the formation, andproducing fluids flowing from the formation into the well.

4. A method of heating an oil-beaming formation penetrated by a well tostimulate flow of oil therefrom comprising displacing unheated waterdown the well and into the formation causing initiation of a fracture inthe formation, displacing down the well and into the fracture to deliverthe desired quantity of heat into the formation, shutting in the wellfor a period to disseminate heat through the formation, reducing thepressure in the well to a pressure lower than the pressure in theformation, and producing fluids flowing from the formation into thewell.

References Cited UNITED STATES PATENTS 1,237,139 8/1917 Yeomans 166-113,042,114 7/1962 Willman 166-11 3,125,072 3/1964 Brandt et al.

3,167,120 1/1965 Pryor 166-11 X 3,284,281 11/1966 Thomas 166-40 X3,288,214 ll/1966 Winkler 166-40 3,330,353 7/1967 Flohr 166-40 STEPHENI. NOVOSAD, Primary Examiner U.S. cll X.R,

